Here is a quote from Mr. Tooley (thanks EconTalk for the transcript) to start you off:

I was in Hyderabad in South Central India. I was there doing consultancy work for the International Finance Corporation, the private arm of the World Bank. I was looking at elite private education, private education for the middle classes and the rich, because I’d become an expert in private education–that was my area of research. I was dissatisfied with this because for whatever reason, I was drawn to serving the poor. That’s what I felt my life should be about. And here I was looking at private education for the rich.

So, on a day off from my consultancy, I wandered down into the slums of the Old City; and sure enough–I had a hunch about what I might find, and I found a private school. A school, charging in those days what would be the equivalent of $1 U.S. dollar per month, serving a hundred children. I met these people; and then I wandered down another alleyway and found another school. And soon I was in contact with a federation of 500 of these low-cost private schools in these poor, largely Muslim areas of the old city of Hyderabad.

It was an amazing finding for me, because suddenly the two parts of my life came together. I could work concerning the poor, low income families and I could be exploring private education, too. But more than that, this seemed very exciting. Poor people were using private schools. Why? Why has no one told me about this? What’s going on here. And so I began a really exciting time in my life.